Bench-Top Options
PUTTING ANY GREENHOUSE into operation requires an investment in making or acquiring a number of accessories. At the very least, you’ll need potting soil, pots, trays, tools, and a place to pot plants (possibly a potting bench), but you may also need growing beds or benches, a germination setup or growing chamber, tool racks and other storage for tools and supplies (possibly a secure storage cupboard or locker), a wheelbarrow or cart, window screens and other supplies for insect control, and other accessories. While some of these must be purchased, many of them can be made or improvised by a competent do-it-yourselfer.
Most people like to set their potted plants on benches in the greenhouse because raising the plants allows air to circulate around them. In addition, plants on benches are raised above the layer of coldest air near the floor of the greenhouse. As part of their greenhouse kits, many manufacturers offer benches that fasten onto the greenhouse structure. When buying a greenhouse kit, check to see if such benches are included and if they are strong enough to hold the weight of a large number of plants. If a bench buckles and it’s supported by the structure, it can distort the greenhouse frame and cause leaks or air gaps. The best benches are freestanding. These come in many shapes and forms.
Types of benches range from a homemade wooden table sitting on concrete blocks to a simple potting bench to a sophisticated hydroponic bench complete with vents and drains, used by retail plant growers.
The most basic greenhouse bench can be made from 2×4 supports with 2×6s or 2×8s used as a top. For many greenhouses, however, a heavy lumber bench like this is too clumsy, in which case a lighter top of 1×4 or 1×6 cedar can be used. You can also make the bench top from 1-inch wire mesh to allow dirt to fall through and light and fresh air to circulate around and under plants. Mesh is also easier to clean and keep free of insect eggs and disease than is a wooden bench surface. Wire mesh is usually galvanized after it has been welded, so it should last for a few years in the humid greenhouse environment. Do not use mesh that has not been galvanized, and beware of damaging the galvanized covering when stapling the mesh to its supports. Bench-top mesh comes in widths from 2 feet to 8 feet and lengths up to 100 feet. To make your own bench tops, it may be economical to buy a roll of the material.
Another bench-top option is expanded metal mesh. This surface has diamond-shaped openings and comes in sizes from 2 feet by 6 feet to 6 feet by 8 feet. It is relatively simple to staple this material to a wooden frame.
It’s also easy to make the frame for a mesh-topped bench. Two of the most common bench frame materials are metal galvanized pipe and steel-slotted galvanized angle bar. To build a metal pipe bench, buy the necessary parts based on accurate measurements of desired width and height. The structure will probably settle on four or six flanges for the base with screw-in legs. At the top you can use either two- or three-way angles to frame it. To connect the pipes, you can either use slip fittings or add threads to pipe pieces cut to the right length. (A plumber can help you cut threads on the pipe ends.) Once everything is assembled, the mesh frame can be stapled to a wooden frame fastened to the top of the pipe frame with pipe brackets.
You can make an angle-bar bench by first purchasing 1-inch or 11⁄2-inch slotted galvanized angle bar at your local hardware store, then bolting together all the pieces. Don’t weld the pieces because welding galvanized metal causes the emission of toxic fumes and the heat generated by the process destroys the galvanized finish (meaning you’ll have to paint the bench later).
Of course, you may not want to go to the time and expense of building either a wooden or a metal bench. In this case, there are snap-together heavy-duty plastic benches (some are made by the manufacturer Benchmaster). A typical 3-foot by 8-foot bench can cost less than $100. The recycled UV-stabilized plastic is durable and readily assembled, can be hosed off easily, and will support heavy loads. In addition, should you decide to change your bench configuration, these benches can be disassembled and reassembled in minutes.
Shelves are an essential part of most greenhouses. In my lean-to greenhouse with a back wall that’s almost 12 feet high, I find that shelves allow me to place a large number of potted plants in areas where they would not normally be located (though I need a ladder to reach the topmost shelves).
Commercially made brackets make the best shelf supports. You can use fixed brackets screwed directly to the wall or frame of the greenhouse, but slotted shelf standards allow you to adjust shelf heights as plants grow.
Shelves can be made of any material, as long as it can support the load of lots of filled pots after plants have been watered. Some options are cedar, painted wood, and expanded metal, but I’ve also found that vinyl-coated-wire closet shelves work well in the greenhouse. They are lightweight, have a lip along the front edge, lock into place, and can support a fairly heavy load. They come in various lengths from 2 feet to 10 feet. They should be painted, however, before you install them in the greenhouse. The vinyl layer on the shelf might stand up to closet use, but it doesn’t seem to last for more than two or three seasons in a greenhouse. Once the layer is broken or chipped, the metal underneath rusts quite quickly.
A conventional kit greenhouse may not have many places to locate shelves; you may have to compromise on where you put them. Possible shelving locations is one of the factors you should check for when you buy a greenhouse. Some extrusions have slots that allow you to install shelf supports from the ceiling or walls in any configuration. On wood-framed greenhouses, the shelf supports or brackets can be screwed directly to the frame, but beware of fastening too many shelves on greenhouse framing. It may not be designed to hold the weight.
If you decide to grow directly in the ground inside the greenhouse, its best to divide growing areas with lumber or with one of the brands of plastic or composite lumber that are available now and are reputed to be rot-proof. In my greenhouse I use half-width concrete blocks (they’re half the width of regular concrete blocks) or bricks to divide the growing beds from the walkways.
When developing a growing bed, the trick is to improve the soil to suit the plants you want to grow. For example, most brassicas, onions, and corn are heavy feeders, so you’ll need plenty of manure and soil supplements. In my cold greenhouse, I can dig these amendments into the beds any time during the winter and leave them to break down. Because greenhouse beds are not subjected to snow and rain, the supplements will not leach out of the soil.
If you plan to grow tomatoes in your greenhouse, manure is the wrong thing to put in to the soil. Adding manure yields lush, green healthy plants but no fruit. Instead, add phosphates and potash to ensure that tomatoes will set fruit early and for a long season. Any good gardening book can tell you the precise amounts that you need and what types are best for your soil.
If you’ve excavated for a greenhouse foundation, much of the soil in the greenhouse may be subsoil left over from the excavation. In my opinion, the best way to improve this soil is to dig it out and replace it with a mixture of manure, compost, screened loam, sand, and any other additives that might be necessary. Once you’ve improved your greenhouse soil, test it. The local extension service can usually perform the test or walk you through the steps necessary to do it yourself.
Raised beds in the greenhouse are especially serviceable and accessible by those in wheel-chairs or those who cannot bend down easily to work in-ground beds — and they can be built as high as necessary. In a greenhouse, it is relatively simple to make raised beds provided the decision to install them is made early on in the design process.
Raised beds in the greenhouse are especially serviceable and accessible by those in wheelchairs or those who cannot bend down easily to work in-ground beds — and they can be built as high as necessary.
The major choice involved in a raised bed is what material you will use for its support structure. Instead of lumber, I use stone for some bed walls and half-width concrete bricks for others (to allow more space for the growing medium). It’s also important to determine how you plan to fill the raised bed area. If you want hot beds (heated growing beds), you will need to refill them every fall (because they are active for only 4 to 6 weeks at a time), which can be a real chore if you haven’t planned out how you are going to do it. The process for emptying and refilling raised beds involves being able to get a large wheelbarrow right next to the bed, removing the material that supports one end of the bed, and shoveling the soil out of and into the bed (or you can use a small power vehicle such as a Bobcat if your greenhouse space allows). The best time to make these decisions about activities that require room to navigate is before the greenhouse is built, when you still have the design on paper.
The tools I use in my greenhouse are stored on a rack in a small annex to the structure, which my wife refers to as the potting shed. Along with tools, this small area contains all the fertilizers, plant pots, and insecticides that I use in the greenhouse. Anything that is at all hazardous or potentially harmful (such as fertilizers and insecticides) is kept in cupboards located high on the wall, out of reach of small children.
Following are some tools and equipment that are basic to most greenhouse operations.
I modified a rake, small shovel, and hoe for use in the greenhouse by cutting down the handles to 3 feet — long enough to work in the raised beds but not so long that I risk poking the handle through a window when I’m working in the cramped space.
I also use several trowels in the greenhouse. Some have short handles (making them easy to use with one hand); others have longer handles to reach the rear of the raised beds. The best tools I own are made by the English toolmaker Burgon and Ball (see Resources). They’re all stainless steel and are made for use in close spaces. These tools now have pride of place on my greenhouse tool board.
Other essential tools are a dustpan and brush, although I have to admit that I drag the shop vacuum cleaner into the greenhouse for a major spill. I also always carry clippers when working in the greenhouse; you never know when you’ll have to trim a plant or clip an errant root. Another very useful tool is a squeegee, for cleaning the glazing. (To get the maximum amount of light into the greenhouse, the windows should be cleaned regularly inside and out; see chapter 12.) I have two: a long-handled one for the roof glass and a short-handled one for the sides.
Twine is essential in a well-maintained greenhouse. I use degradable hemp twine so that it can be discarded at the end of the season along with the plants it ties to stakes or overhead supports. Twine can also be tied to the greenhouse rafters so that vines can grow up it. It can be used to hold open windows or doors temporarily and I’ve used it to tie down the cover of a hoop house during strong winds.
These bolts screwed into the rafters of wood-frame greenhouses serve as handy anchors for hanging baskets. I make up twelve to fifteen 18-inch hanging baskets each February (I buy them wholesale from my garden supplier) and hang them from eyebolts in the greenhouse rafters. The eyebolts are placed directly over growing beds so that any water that drains from them falls right to the plants in the beds. In spring, when I move the hanging baskets to the deck, I tie long lengths of twine to the eyebolts and train tomatoes, beans, and peas up them.
Another important greenhouse tool is a riddle. Sometimes called a screen or sieve, this tool can be used to screen potting soil for starting fine seeds. It can also be used to separate weeds and roots from good, reusable greenhouse soil and for sifting small stones from fresh loam. In the greenhouse I use a small circular riddle with different-sized meshes, available from Lee Valley Tools (see Resources).
Sprayers are also useful in the greenhouse. I use three sizes: a small, half-gallon one for locally spraying plants that have special requirements, such as a foliar spray; a larger, 2-gallon sprayer reserved for pesticide or herbicide applications (which is never used for anything else); and a 5-gallon backpack sprayer for spraying fruit trees outdoors. I often spray the greenhouse trees using this after I’ve moved them to their summer locations and before they go back in the greenhouse in the fall.
I regularly use several kinds of barrows and carts in the greenhouse — a wheelbarrow, a garden cart, and a specially made flat-decked cart — to tote heavy items into and out of the structure. If your greenhouse has a concrete floor, you might want to invest in a wheeled dolly to help move heavy plants. Available at most hardware stores and home centers, these are made of wood and have swiveling casters. Car stores have similar products called creepers to help you get under a vehicle while lying on your back.
If your greenhouse does not have a concrete floor, you may have to use a large, wheeled garden cart to move things around, which usually means lifting heavy pots into and out of it. Another useful cart is the type of two-wheeled dolly that delivery men use to bring in heavy parcels, but if you’re moving a big tree on one of these, you’ll need to tie it down to keep it stable and upright while you move it.
An essential greenhouse tool is a thermometer. The best kind is a maximum/minimum thermometer that shows and records the daytime high and nighttime low temperatures. I also like to have a pair of large-dial thermometers (one at each end), which allow me to view the temperature at a glance from outside the building. Finally, I have a 24-inch-long thermometer to check the temperature of the compost pile. It looks like a larger version of the thermometer that you stick in a roasting chicken to see if it’s done. With it I can determine when the compost pile and hot beds have cooked sufficiently and are cooling down. You can also get a number of remote sensing thermometers that allow you to monitor your greenhouse from indoors. These are sold by most greenhouse suppliers, and even Radio Shack has one.
Replace the pneumatic tire of your wheelbarrow with a solid rubber tire, available from hardware stores for about $30. A solid tire means you won’t have to worry about checking air pressure or puncturing it while working.
Last but not least is the tool used most often in the greenhouse: a good watering can. It’s easy to dip this tool into the greenhouse water tank or fishpond, add a teaspoon of fertilizer, and water the potted plants. I use a 2-gallon watering can with an adjustable spout, but I also have a 1-gallon can from Lee Valley Tools with a long spout for reaching plants at the rear of the beds.
A variety of fittings for the end of your garden hose can be useful in the greenhouse. A pressure-breaker hose on the end of a long wand (it looks like a walking stick with a large, circular head on the end) is helpful for watering hanging baskets. When you turn on the garden hose, this attachment reduces the pressure of the water coming out of the end so that you don’t blast dirt out of the garden beds or hanging baskets.
An attachable fertilizer jar available from most garden centers can be used to fertilize while you water. And you’ll need a powerful sprayer to blast dirt off the greenhouse glass and a head with a gentler spray that you can use to water plants in growing beds.
Do you start your own plants from seeds? If you haven’t up to now, owning a greenhouse may prompt you to start all your plants. Seeds start best when they have a favorable temperature, and different types of plants require different temperatures. For example, many flower seeds prefer 70°F to 75°F to germinate, while wild-flowers tend to germinate at temperatures of 65°F to 70°F. Brassicas and other green-leafed vegetables prefer 65°F to 72°F, while tomatoes like 75°F to 80°F. Obviously, if you can satisfy the germination requirements of each of these plants, you’ll be able to grow more seedlings.
To make a seed-starting box or germination chamber, you’ll first have to make a frame capable of supporting the weight of one or two 4-foot incandescent 15- to 40-watt lightbulbs. The inside of the frame is covered with foil-faced polyisocyanurate, available from a building supplier. This insulation keeps the box warm and the foil facing reflects light back toward the plants. If you make the box wide enough to hold two seed trays and the lights above them, it should be at least 4 feet wide and 22 inches deep on the inside, which allows room to place two 22-inch flats end to end under a single light fixture. It should be tall enough inside only to prevent the lightbulbs’ heat from burning the plants; about 24 inches tall is usually sufficient. I added a couple of holes in the top and bottom to allow air to circulate and extra heat to vent from the chamber, though I use 40-watt lights; you may find that you don’t need air holes if you use lightbulbs that are only 15 watts.
The lights are operated by a timer and stay on for a set period. The “on” period depends upon the type of seed you want to germinate. For example, the light is left on for up to 20 hours a day for impatiens seeds because they need almost continuous light to germinate. Primulas also require a long period of light to germinate. As soon as seeds have germinated, I move the trays to a growing area, where the lights are turned on for up to 14 hours a day. This frees up the germinating chamber for new plants. I find that I keep the germinating chamber going for 3 to 4 months in the early part of the year. I start using it around December with perennial flowers, followed by annuals, vegetables such as leeks and onions that require a long growing period, and then the faster-growing vegetables so that by mid-April (in Rhode Island) the plants are ready to go out into the cool greenhouse and from there into the garden.
A seed-starting or germination chamber
My growing chamber, located in the basement of my house, allows me to grow seedlings when it’s snowing outside. Here in Rhode Island, I start pepper and eggplant seedlings in the middle of January, while I start many perennial flower seedlings in late fall and then move them to the greenhouse for the winter.
The growing chamber was easy to build. It uses four 40-watt fluorescent shop fixtures (two tubes per fixture) on each level (each with a cool white tube and a warm white tube for the best growing light). The area of each level is slightly more than 4 feet by 4 feet, which allows eight flats of seedlings per level. The sides are framed with 2×4s with furring strips bridging the gap between both sides. The sides of the growing chamber are lined with foil-faced insulation to reflect heat back to the plants. If the area around your growing frame is open, you might want to line it with polyethylene sheeting to keep in heat and humidity. Beware of completely cutting off the air circulation, however. It’s easy for the chamber to build up plenty of heat and moisture and cook your plants. A low-power fan could help circulate the air. In 15 years of using this growing chamber, I have yet to have seeds mildew or damp off, probably because the low heat given off by the lights keeps it warm enough.
I found that placing seed flats directly on the furring strips allows heat from the bottom lights to warm the plants in the flats above. In order to keep flats from falling off the strips, you could install wire mesh over the furring on each level, which still allows rising heat to come through from below to the plants above. I place heat-loving plants such as peppers and tomatoes at the top of the growing chamber and plants that prefer cooler conditions lower down.
On each level, the fixtures are placed a few inches above each seed flat and are controlled by a heavy-duty timer. The idea is to provide the maximum amount of light for the plants, but not to burn them by putting the light fixtures too close. As the plants grow taller, the light fixtures are raised until there is no more space in the chamber to raise them. At this point, the plants are potted up and taken out to the greenhouse.
Be sure to water or mist seedlings as they are growing. You can water them by removing each seed flat or tray one at a time and gently pouring water into each cell. I use a small watering can with lukewarm water. Be very careful when misting trays in place, given that the lights are in close proximity. One drop of water on a light-bulb can be enough to break it. I find that it’s easiest to remove the seed trays to mist them, as I do for watering.
A homemade growing chamber
If you do any kind of serious greenhouse gardening, you’ll need a potting bench, which helps to contain the soil so that it doesn’t go everywhere when you are repotting plants. The best benches have a small sink and running water. A basic bench is not difficult to construct (for a plan, see project 11 in chapter 13).
My bench, framed with 2×2 lumber, stands 36 inches high, although you can adjust the bench dimensions to suit your height or the height of those who will use it. The entire work top, except the front, is enclosed to keep the potting soil on the tabletop. On my bench the corners are curved a bit (they are built up with two layers of 1⁄8-inch plywood — layers of masonite epoxied together will also serve) to form a smooth bend. The curve makes the bench top easy to clean with a single sweep of the brush. Under the bench is storage for potting soil and plant pots, as well as a garbage bin for all those bits and pieces of plants that you snip off when repotting. A covered slot in the bench top directly over the garbage bin allows me to sweep away refuse. A fold-out drawer holds pot labels, felt-tipped pens, and twist ties. Tools are mounted on the outside of the potting table and on its back, where they are near at hand but not in the way when I’m working.
I made the bench top 36 inches deep and 42 inches wide to give myself plenty of work space, but you can adjust the top dimensions to suit the space available. You can also put the bench on casters so that it can be moved around the greenhouse.
A much simpler, movable bench hooks onto the benches over the walkway. This particular model is handy because you often need to pot plants near their location rather than drag them to a stationary potting bench, repot them, and then drag them back to where they’ll grow. It’s made with rounded corners, but instead of having legs, it has cleats on the sides designed to attach to the greenhouse benches. Note that this bench will work only if your walkways are parallel. Otherwise, it will be difficult to fit the bench in place.
A potting bench that attaches to perimeter greenhouse benches across a central aisle. The runners for the bench can be made of metal or wood, though metal slides more easily on the edges of the growing beds.
Storage space is essential for a greenhouse. If you buy fertilizer or potting soil in large bags, you’ll need a place to store them. Sure, they can be kept outside, but in early spring or the middle of winter, when you are about to start seedlings, you’ll have to bring a frozen bag of potting soil into the greenhouse to thaw before you can begin your work. Aside from the delay, the thawing potting soil will draw heat from the greenhouse just when you need it most. In addition to making your work easier, it’s neater to have a space in the greenhouse for storage than to leave supplies piled outside.
Storage can be as simple as shelves (see Shelving) or an open space or air lock, where you can store big bags of potting soil or greenhouse clothes, or it can take the form of a tidier cupboard that can be locked for added safety if any potentially dangerous materials (such as pesticides) are to be stored in it. I store many items — insecticides, sprays, fertilizer, and small pots — in two inexpensive shelf-mounted closets that fit against the back wall of my potting shed. My other storage is located under the deck in my heated pit greenhouse. In this area I can fit up to six large bales of potting soil and a few pots.
The knee wall of many greenhouses offers storage possibilities. If the benches next to this wall are raised to about 36 inches, you’ll find that there’s plenty of space under the bench to store items out of sight or, if the area is glazed, even to grow plants that can live with lower light levels. Plants such as Christmas cacti and amaryllis that are resting, some ground covers, coffee plants, begonias, ferns, and other understory plants can live happily under a bench, provided they are kept warm. If your under-bench plants need more light, you can install waterproof lighting on the underside of the bench. These lights have the added benefit of warming the bench itself, supplying a home for heat-loving plants on top of the bench.
If you are going to store only equipment under the benches, it’s best to block the lower part of a glazed greenhouse to hide the unsightly pile of dozens of pots and bags of potting soil. Of course, a low knee wall of poured concrete will hide stored materials from outside view. On the inside you can install wood-framed mesh doors on the bench in front of the wall to hide the mess but still allow air to circulate.
Remember that any under-bench storage area must be cleaned periodically to keep it free of insects and unnecessary clutter.
Leaving tools in your greenhouse is a sure way to broadcast what you own, increasing the chances that they’ll be stolen. After all, anyone can break a pane of glass to get to your belongings, leaving your plants exposed to cold in the process. Making a storage locker or cupboard for tools, materials, and potentially dangerous garden substances is a good idea. A padlock makes its contents even more secure.
A simple locker can be framed with 2×2 lumber and covered with plywood. Be sure to measure your tools before beginning construction; the locker should be wide enough to hold your widest tool, tall enough to fit your longest rake or spade handle, and deep enough to allow space for all your tools and bigger items.
Making a storage locker for tools, materials, and potentially dangerous garden substances is a good idea. A padlock makes its contents even more secure.
If you have a small hobby greenhouse or a kit greenhouse that has no room at all for a storage locker, consider another structure, such as a garden shed, for storage. A separate shed can also store larger lawn and garden equipment and can be easily locked. It might also have a wider door (3 feet or more) to allow easy access for wheel-barrows and other equipment.
I wear old clothes when I go into the greenhouse. Usually, I have no idea what needs to be done when I enter, but a plant might need repotting or trimming or moving, and often I end up getting dirty. If you don’t want to change your clothes entirely before beginning work, hang an apron or coveralls in the greenhouse where you can put them on easily (perhaps on a peg or hook just inside the door). A rubber apron allows you to spill water and wet potting soil without worry or discomfort. You may also want to wear light summer clothes while you work in your greenhouse. These structures can become hot in the sunlight, reaching temperatures of more than 80°F even in mid-winter. Besides being comfortable in this warm environment, summer clothing can give a real boost to the spirit on icy winter days. Avoid loose-fitting clothing, however. It can catch on branches, which can bring even great potted plants crashing to the ground.
If you are going to pot up plants or fill seed flats, you may want to wear a pair of rubber gloves. The best for working with water or damp soil are the rubber gloves used for dishwashing. With their longer cuffs, they keep your wrists and arms clean, too. Finally, a pair of watertight or rubber boots can be useful if you plan to spray water in your greenhouse; if your greenhouse work is reasonably dry, however, normal gardening shoes will do.
Even the most “benign” pesticides such as dormant oil can irritate the skin and pose a threat, especially if sprayed in an enclosed area. If you plan to spray greenhouse plants with chemicals or any form of pesticide, you’ll need a respirator, a face mask or goggles, and rubber gloves. Consider investing in a suit with a hood to protect you all over. (I prefer to wear a Tyvek suit.) The respirator should have a filter suitable for the chemical that you’re spraying. (Read all manufacturer’s instructions on content and safety before you begin applying any material.) You can buy a respirator for $50 to $75 and filters for a few dollars more. The investment is well worth it.
Once you have sprayed any pesticides, it’s important to stay out of the greenhouse for a few hours to give the spray time to dissipate.
Most hobby greenhouses will have insects at various times during the year. Whiteflies and aphids are common pests that can be eliminated by spraying with any insecticide, although I prefer to use biological or organic controls such as ladybugs and praying mantis unless the infestation gets out of hand. Remember that the first line of defense in any greenhouse is to screen open windows. This helps to keep insects out, although some insects will get through larger mesh. Dense mesh, however, blocks substantial light and air, so you’ll have to find a balance that controls insects without compromising the light and air environment for your plants.
If you do have a plant that becomes infested with insects, it’s best to move it outdoors for spraying, even in the dead of winter. After all, if the plant is going to die because of insect infestation, it’s better to kill it (by exposure to cold weather) or cure it before it infects everything else inside the greenhouse. You can also use a 20- or 30-gallon aquarium as an isolation chamber and spray area for insect-ridden plants. The best plan, however, is to control strictly which plants are taken into the greenhouse and quarantine those that are suspect before they can infect other plants.
If screens fail to keep out a number of insects, you may have to resort to other controls. I use sticky yellow pads to catch and control whitefles, but occasionally I do have to spray when the bugs proliferate. I use Safer’s insecticidal soap and pyrethrin sprays with great success, though heavy application of pyrethrin can leave a gray deposit on all surfaces in the greenhouse and the odor may linger for days or weeks, depending on how much is applied. This can be especially worrisome in an attached greenhouse, where the odors and spray can find their way into your home.